<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script>
		 var n=prompt("请输入一个数字：","0");
		 if(isNaN(n)){
			 alert("不是数字");
		 }else{
			 var i=parseInt(n);
			 alert(i);
		 }
		
		</script>
	</head>
	<body>
	</body>
</html>
